<?php
class Silk_Zgb_Block_Renderer_Refundqty extends Mage_Adminhtml_Block_Widget_Grid_Column_Renderer_Abstract
{
	public function render(Varien_Object $row)
	{
		$id =  $row->getId();
		$collection = Mage::getResourceModel("sales/order_creditmemo_item_collection")->addAttributeToSelect("qty")
		->addFieldtoFilter("parent_id",$id);
		$qty = null;
		foreach ($collection as $item) {
			$qty = $qty+$item->getQty();
		}
		return $qty;
	}
}